Date of Award
Master of Science
Ryan B. Wicker
Radiation thermometry monitoring methods used in powder bed fusion additive manufacturing (PBF-AM) are becoming increasingly more popular for quality assurance and repeatability. The dynamic nature of the PBF process and a lack of accuracy of metrics being captured for temperature monitoring lend great difficulty in the successful implementation of in-situ monitoring. There is currently no data on the emissivity, a metric used in non-contact temperature measurements, for metal powders used in AM. This work describes a method for measuring the spectral emissivity for metal powder sizes commonly used in AM using a multi-wavelength (MW), FMPI SpectroPyrometer, calibrated within the spectral range of 1080nm to 1650nm to determine the feasibility of implementing IR thermography to capture true temperature measurements in situ and provide new information for metal-based AM process simulations and process parameter optimization. The method was developed utilizing an inert glovebox environment and a custom design of an induction heater. The focus of this research was to understand the emissive behavior of metal AM powders at different temperatures using MW pyrometry as a characterization tool. This was done by employing a multi-wavelength pyrometer, internally designed heater, and a glovebox. The objectives of this research can be described as developing an experimental setup and procedure that:(1) Mitigates, or eliminates, radiative environment influence (2) Captures the spectral emissivity of metal powders used in AM, using Inconel 718 powders at different temperatures utilizing a multi-wavelength pyrometer (3) Provides emissivity/absorptivity data and determines the feasibility of implementing infrared thermography in laser powder bed fusion processes Initially, a custom design of an LC-150 Standard Glovebox System (LC Technology Solutions, MA, USA) was made to include two viewports at the top of the system that would allow for a direct line of sight for the pyrometer. A fixture attached to one of the viewports housed the pyrometerâ??s optic with a silicon carbide tube affixed to the other end that extended down towards the target (powder). This unobstructed line of sight allowed for the SpectroPyrometer from FAR Associates (Macedonia, OH, USA) to be positioned normal to the sample surface. Prior to the heating of the powders, a calibration using a NIST traceable blackbody was performed. Measurements of three different powder diameter ranges of Inconel 718 (15-53Âµm, 45-105Âµm, and 45-150Âµm) using their apparent and tap densities were captured as they were progressively heated in steps of 400â??, then 500â??, and finally 600â??. Values of the spectral emissivity captured during experimentation were like those of the Thermophysical Properties Research Center (TPRC) Data Series Vol. 7, the largest database of emissivity values, and reasons for deviation are given within the work. The results showed instances in which a graybody assumption would be valid, an assumption (along with the actual value for emissivity) needed for accurate temperature measurements via IR thermography. Future work will include a higher range of temperatures and different powder alloys commonly used in PBF-AM.
Recieved from ProQuest
Levario, Emmanuel, "A Method For Measuring The Spectral Emissivity Of Metal Powders At Different Temperatures And Applications In Laser Powder Bed Fusion" (2023). Open Access Theses & Dissertations. 3814.